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Introduction Bones and joints do not produce movement
The human body has more than 600 individual muscles Muscles cause bones and supported structures to move by alternating between contraction and relaxation You will focus on the differences among three muscle tissue types, the structure of skeletal muscles, muscle actions, and the names of skeletal muscles.
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Functions of Muscle Muscle has the ability to contract, permitting muscles to perform various functions Functions: Movement Stability Control of body openings and passages Heat production Click for Larger View
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Movement Skeletal muscles Smooth muscle Cardiac muscle
Attached to bones by tendons Cross joints so when they contract, bones they attach to move Smooth muscle Found on organ walls Contractions produce movement of organ contents Cardiac muscle Produces atrial and ventricular contractions This pumps blood from the heart into the blood vessels
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Stability Hold bones tightly together
Stabilize joints Small muscles hold vertebrae together Stabilize the spinal column
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Control of Body Openings and Passages
Sphincters Valve-like structures formed by muscles Control movement of substances in and out of passages Example: A urethral sphincter prevents or allows urination
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Heat Production Heat is released with muscle contraction
Helps the body maintain a normal temperature Moving your body can make you warmer if you are cold
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Apply Your Knowledge RIGHT! F T T F F True or False:
___ Skeletal muscles are attached to bones by ligaments. ___ Contractions of smooth muscle produce movement of organ contents. ___ Cardiac muscle produces atrial and ventricular contractions. ___ Sphincters control movement of substances out of passages. ___ Heat is released as muscles relax. ANSWER: tendons F T T in and out F RIGHT! F contract
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Types of Muscle Tissue Muscle cells Myocytes called muscle fibers
Sarcolemma – cell membrane Sarcoplasm – cytoplasm of cell Myofibrils – long structures in sarcoplasm Arrangement of filaments in myofibrils produces striations
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Types of Muscle Tissue (cont.)
Muscle Group Major Location Major Function Mode of Control Skeletal Muscle Attached to bones and skin of the face Produces body movements and facial expressions Voluntary Smooth Muscle Walls of hollow organs, blood vessels, and iris Moves contents through organs; vasoconstriction Involuntary Cardiac Muscle Wall of the heart Pumps blood through heart
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Skeletal Muscle Muscle fibers respond to the neurotransmitter acetylcholine Causes skeletal muscle to contract Following contraction, muscles release the enzyme acetylcholinesterase Breaks down acetylcholine Allows muscle to relax
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Smooth Muscle Multiunit smooth muscle Visceral smooth muscle
In the iris of the eye and walls of blood vessels Responds to neurotransmitters and hormones Visceral smooth muscle In walls of hollow organs Responds to neurotransmitters AND Stimulate each other to contract so that muscle fibers contract and relax together in a rhythmic motion – peristalsis
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Smooth Muscle (cont.) Peristalsis – rhythmic contraction that pushes substances through tubes of the body Neurotransmitters for smooth muscle contraction Acetylcholine Norepinephrine Will cause or inhibit contractions, depending on smooth muscle type
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Cardiac Muscle Intercalated discs
Connect groups of cardiac muscle Allow the fibers in the groups to contract and relax together Allows heart to work as a pump Self-exciting – does not need nerve stimulation to contract Nerves speed up or slow down contraction
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Cardiac Muscle (cont.) Neurotransmitters
Acetylcholine – slows heart rate Norepinephrine – speeds up rate
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Apply Your Knowledge Very Good! Match the following: ANSWER:
___ Self-exciting A. Skeletal muscle ___ Contract in response to B. Smooth muscle acetylcholine C. Cardiac muscle ___ Stimulate each other to contract ___ Peristalsis ___ Slowed by acetylcholine ___ Voluntary movement ANSWER: C A B B Very Good! C A
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Production of Energy for Muscle
ATP (adenosine triphosphate) A type of chemical energy Needed for sustained or repeated muscle contractions Muscle cells must have three ways to store or make ATP Creatine phosphate Rapid production of energy Aerobic respiration Uses body’s store of glucose Lactic acid production Small amounts of ATP ATP = energy
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Lactic acid which builds up
Oxygen Debt Develops when skeletal muscles are used strenuously for several minutes and cells are low in oxygen Pyruvic acid Converts to Lactic acid which builds up Muscle fatigue To liver for conversion to glucose, requiring more energy and oxygen to make ATP Oxygen debt
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Muscle Fatigue Condition in which a muscle has lost its ability to contract Causes Accumulation of lactic acid Interruption of the blood supply to a muscle A motor neuron loses its ability to release acetylcholine onto muscle fibers
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Yippee! Apply Your Knowledge Match the following:
___ Rapid production of energy A. Lactic acid ___ Needed for sustained or B. Pyruvic acid repeated muscle contractions C. ATP ___ Uses body’s store of glucose D. Aerobic ___ Muscle fatigue respiration ___ With strenuous exercise, E. Creatine converts to lactic acid phosphate ANSWER: E C D A B Yippee!
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Structure of Skeletal Muscles
The major components of the muscular system Composition Connective tissue Skeletal muscle tissue Blood vessels Nerves
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Connective Tissue Coverings
Fascia Covers entire skeletal muscles Separates them from each other Tendon A tough, cord-like structure made of fibrous connective tissue Connects muscles to bones Aponeurosis A tough, sheet-like structure made of fibrous connective tissue Attaches muscles to other muscles
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Connective Tissue Coverings (cont.)
Epimysium A thin covering that is just below the fascia of a muscle and surrounds the entire muscle Perimysium Connective tissue that divides a muscle into sections called fascicles Endomysium Covering of connective tissue that surrounds individual muscle cells
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Apply Your Knowledge Excellent! D E A B F C Match the following:
__ Thin covering under the fascia that surrounds the muscle __ Separates muscles from each other __ Connects muscles to bones __ Divides a muscle into sections called fascicles __ Surrounds individual muscle cells __ Attaches muscles to other muscles ANSWER: D Tendon Perimysium Aponeurosis Epimysium Fascia Endomysium E A B F C Excellent!
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Attachments and Actions of Skeletal Muscles
Actions depend largely on what the muscles are attached to Attachment sites Origin – an attachment site for a less movable bone Insertion – an attachment site for a more movable bone
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Attachments and Actions (cont.)
Movement usually produced by a group of muscles Prime mover (agonist) – muscle responsible for most of the movement Synergists – muscles that help the prime mover by stabilizing joints Antagonist – muscle that produces movement opposite to prime mover Relaxes when prime mover contracts
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Figure of Body Movements
Plantar flexion – pointing the toes down Abduction – moving a body part away from the anatomical position Adduction – moving a body part toward the anatomical position Flexion – bending a body part Extension – straightening a body part Hyperextension – extending a body part past the normal anatomical position Dorsiflexion – pointing the toes up Figure of Body Movements
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Body Movements (cont.) Back
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Body Movements (cont.) Circumduction – moving a body part in a circle Pronation – turning the palm of the hand down Supination – turning the palm of the hand up
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Body Movements (cont.) Inversion – turning the sole of the foot medially Eversion – turning the sole of the foot laterally Retraction – moving a body part posteriorly Protraction – moving a body part anteriorly
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Body Movements (cont.) Elevation – lifting a body part; for example, elevating the shoulders as in a shrugging expression Depression – lowering a body part; for example, lowering the shoulders
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Correct! Apply Your Knowledge
The doctor has asked you to abduct the patient’s leg so he can see the patient’s wound. In order to position the patient correctly, what will you have to do? ANSWER: Move the patient’s leg away from its position in the anatomical position. Correct!
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Major Skeletal Muscles
The muscle name indicates Location Size Action Shape OR Number of attachments of the muscle As you study muscles, you will find it easier to remember them if you think about what the name describes.
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Muscles of the Head Sternocleidomastoid Splenius capitis Frontalis
Pulls the head to one side Pulls the head to the chest Frontalis Raises the eyebrows Splenius capitis Rotates the head Allows it to bend to the side Orbicularis oris Allows the lips to pucker
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Muscles of the Head (cont.)
Orbicularis oculi Allows the eyes to close Zygomaticus Pulls the corners of the mouth up Platysma Pulls the corners of the mouth down Masseter and temporalis Close the jaw
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Arm Muscles Pectoralis major Latissimus dorsi
Pulls the arm across the chest Rotates and adducts the arms Latissimus dorsi Extends and adducts the arm and rotates the arm inwardly
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Arm Muscles (cont.) Deltoid Subscapularis Infraspinatus
Abducts and extends the arm at the shoulder Subscapularis Rotates the arm medially Infraspinatus Rotates the arm laterally
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Arm Muscles (cont.) Biceps brachii Brachialis Brachioradialis
Flexes the arm at the elbow Rotates the hand laterally Brachialis Brachioradialis Flexes the forearm at the elbow
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Arm Muscles (cont.) Triceps brachii Supinator Pronator teres
Extends the arm at the elbow Supinator Rotates the forearm laterally (supination) Pronator teres Rotates the forearm medially (pronation)
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Wrist, Hand, and Finger Muscles
Flexor carpi radialis and flexor carpi ulnaris Flex and abduct the wrist Palmaris longus Flexes the wrist Flexor digitorum profundus Flexes the distal joints of the fingers, but not the thumb
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Wrist, Hand, and Finger Muscles (cont.)
Extensor carpi radialis longus and brevis Extend the wrist and abduct the hand Extensor carpi ulnaris Extends the wrist Extensor digitorum Extends the fingers, but not the thumb
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Respiratory Muscles Diaphragm External and internal intercostals
Separates the thoracic cavity from the abdominal cavity Its contraction causes inspiration External and internal intercostals Expand and lower the ribs during breathing
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Click for View of Abdominal Muscles
External and internal obliques Compress the abdominal wall Transverse abdominis Also compresses the abdominal wall Rectus abdominis Flexes the vertebral column Compresses the abdominal wall Click for View of Abdominal Muscles
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Click for View of Pectoral Girdle Muscles
Trapezius Raises the arms Pulls the shoulders downward Pectoralis minor Pulls the scapula downward Raises the ribs Click for View of Pectoral Girdle Muscles
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Leg Muscles Iliopsoas major Gluteus maximus Gluteus medius and minimus
Flexes the thigh Gluteus maximus Extends the thigh Gluteus medius and minimus Abduct the thighs Rotate them medially
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Leg Muscles (cont.) Adductor longus and magnus
Adduct the thighs Rotate them laterally Biceps femoris, semitendinosus, and semimembranosus Known as the hamstring group Flex the leg at the knee Extend the leg at the thigh
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Leg Muscles (cont.) Rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius Extend the leg at the knee Sartorius Flexes the leg at the knee and thigh Abducts the thigh, rotating the thigh laterally but rotating the lower leg medially
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Ankle, Foot, and Toe Muscles
Tibialis anterior Inverts the foot and points the foot up (dorsiflexion) Extensor digitorum longus Extends the toes and points the foot up Gastrocnemius Flexes the foot and flexes the leg at the knee
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Ankle, Foot, and Toe Muscles (cont.)
Soleus Flexes the foot Flexor digitorum longus Flexes the foot and toes
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Bravo! Apply Your Knowledge
Your patient complains of hurting his hamstring when running today. You would look at what part of the leg, and what muscles would be involved? ANSWER: You would look at the back of his leg, and the muscles involved would be the biceps femoris, semitendinosus, and semimembranosus. These three muscles are known as the hamstring group. Bravo!
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Muscle Strains and Sprains
Strains – injuries due to over-stretched muscles or tendons Sprains – more serious injuries that result in tears to tendons, ligaments, and/or cartilage of joints RICE is recommended treatment for either Rest Ice Compression Elevation
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Muscle Strains and Sprains (cont.)
Prevention Warm up muscles A few minutes before an intense activity raises muscle temperature and makes muscle more pliable Stretching Improves muscle performance and should always be done after the warm-up or after exercising Cooling down or slowing down Before completely stopping prevents pooling of blood in the legs and helps remove lactic acid from muscles
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Aging and the Musculoskeletal System
Contractions become slower and not as strong Dexterity and gripping ability decrease Mobility may decrease Assistive devices helpful Routine exercise Swimming Physical therapy
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Diseases and Disorders of the Muscular System
Description Botulism Affects the gastrointestinal tract and various muscle groups Fibromyalgia Fairly common condition that causes chronic pain primarily in joints, muscles, and tendons Muscular dystrophy Inherited disorder characterized by muscle weakness and a loss of muscle tissue Myasthenia gravis Autoimmune condition in which patients experience muscle weakness
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Diseases and Disorders of the Muscular System (cont.)
Description Rhabdomyolysis A condition in which the kidneys become damaged after serious muscle injuries Tetanus (lockjaw) Painful inflammation of a tendon and the tendon-muscle attachment to a bone Torticollis (wryneck) Acquired or congenital; spasm or shortening of the sternocleidomastoid muscle; head bends to affected side and chin rotates to opposite side Trichinosis An infection caused by parasites (worms)
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Apply Your Knowledge Good Job!
The doctor has told your patient that his son has muscular dystrophy disorder. What is muscular dystrophy? ANSWER: Muscular dystrophy is an inherited disorder characterized by muscle weakness and a loss of muscle tissue. Good Job!
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In Summary 22.1 The functions of muscles include movement, stability, control of body openings and passages, and the production of heat The three types of muscle tissue are striated voluntary skeletal muscle, smooth involuntary visceral muscle, and specialized striated and involuntary cardiac muscle Peristalsis is the rhythmic contraction produced by smooth muscle to push substances through various tubes in the body.
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In Summary (cont.) 22.4 Muscles create energy in three ways. Creatine phosphate is a rapid method for muscles to create energy, aerobic respiration uses stored glucose to produce ATP in the Krebs cycle, and lactic acid production occurs when a cell is low in oxygen and coverts pyruvic acid to lactic acid Skeletal muscle is composed of connective tissues, skeletal muscle tissue, blood vessels, and nerves. The coverings of skeletal muscles include fascia, tendon, aponeurosis, epimysium, perimysium, and endomysium.
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In Summary (cont.) 22.6 The origin of a muscle is the attachment site of the muscle to the less movable bone during muscle contraction. The insertion of a muscle is the attachment site for the muscle to the more movable bone during muscle contraction The body movements produced by skeletal muscles include flexion, extension, hyperextension, dorsiflexion, plantar flexion, abduction, adduction, rotation, circumduction, pronation, supination, inversion, eversion, retraction, protraction, elevation, and depression.
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In Summary (cont.) 22.8 The major muscles of the head are sternocleidomastoid, splenius capitis, frontalis, orbicularis oris and oculi, zygomaticus, platysma, masseter, and temporalis. The upper extremity muscles include pectoralis major, latissimus dorsi, deltoid, subscapularis, biceps brachii, brachialis, brachioradialis, triceps brachii, supinator and pronator teres, flexor carpi radialis and ulnaris, plamaris longus, flexor digitorum profundus, extensor carpi radialis longus and brevis, and extensor digitorum. The major respiratory muscles are the diaphragm and the external and internal intercostals.
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In Summary (cont.) 22.8 (cont.) The abdominal muscles include external and internal obliques, transverse abdominis, and rectus abdominis. The pectoral girdle muscles include trapezius and pectoralis minor. The muscles of the lower extremity include iliopsoas major; gluteus maximus, medius, and minimus; adductor longus and magnus; biceps femoris; semitendinosus and semimembranosus; rectus femoris; vastus lateralis, medius, and intermedius; sartorius; tibialis anterior; extensor digitorum longus; gastrocnemius; soleus; and flexor digitorum longus.
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In Summary (cont.) 22.9 Strain injuries involve injuries to muscles and/or tendons. Sprains are more serious injuries that result in tears to tendons, ligaments, and/or the cartilage of joints The common diseases of aging include arthritis, fractures, osteoporosis, and muscular decline. Aging causes a decline in strength and speed of muscle contractions. Dexterity and gripping abilities lessen and mobility often decreases related to skeletal and muscular decline.
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In Summary (cont.) 22.11 The diseases of the muscular system, as well as their symptoms and treatments, vary widely and are discussed in the Pathophysiology section of this chapter. Some of the common diseases discussed include botulism, fibromyalgia, muscular dystrophy, myasthenia gravis, tendonitis, tetanus, and torticollis.
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End of Chapter 22 Everyone has a ‘risk muscle.’ You keep it in shape by trying new things. If you don’t, it atrophies. Make a point of using it at least once a day. ~Roger von Oech
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